The present invention relates to electromechanical valve actuators and more particularly to electromechanical valve actuators that are easy to assemble and include armature stem self-aligning features to ensure that the armature stem stays centered above the valve stem during operation.
As engine technology advances and manufacturers strive to increase engine power, improve fuel economy, decrease emissions, and provide more control over engines, manufacturers are developing electromechanical valve actuators (also known as electromagnetic valve actuators or EMVA) to replace camshafts for opening and closing engine valves. Electromechanical valve actuators allow selective opening and closing of the valves in response to various engine conditions.
Electromechanical valve actuators generally include two electromagnets formed from a lamination stack and an embedded power coil. A spring loaded lever armature located between the electromagnets is movable between the electromagnets as the power coils are selectively energized to create a magnetic force to attract the armature to the energized electromagnet. The surface of the electromagnets to which the armature is attracted when the power coil of an electromagnet is energized is generally referred to as a pole face. The armature is operationally coupled to the valve so that as the armature moves between pole faces in pole-face-to-pole-face operation, the valve is opened and closed.
Electromechanical valve actuators have typically been made as linear electromechanical valve actuators (not shown). Linear electromechanical valve actuators generally draw a substantial amount of power from the alternator and require significant space over the cylinder. In view of the drawbacks associated with linear electromechanical valve actuators, many manufacturers have recently been turning to lever electromechanical valve actuators, which due to their mechanical properties have substantial power savings and are more space efficient. One problem with lever electromechanical valve actuators is that, unlike linear electromechanical valve actuators, due to the mechanical properties of the pivoting lever armature plate, the armature stem also pivots. Pivoting of the armature stem may cause problems during operation, such as, keeping the armature stem, specifically end of the armature stem, aligned with the valve stem. Any misalignment of the armature stem with the valve stem may cause an operational fault, inefficient operation, or excessive wear. Therefore, there is a need for a lever electromechanical valve actuator with self-aligning features to ensure that the armature end of the armature stem stays aligned with the valve stem.